The present invention relates to an improved ring-type binder for binding of loose perforated sheets and the like.
In the past ring binders have been formed of a strip of cylindrically rolled plastic longitudinally split to have two opposed edges. A plurality of teeth are formed along one longitudinal edge which, rolled, overlap the other longitudinal edge forming a plurality of closed rings. The plastic used in such binders have a memory such that when the binder is flexed or bent it is biased to return to its original shape upon removal of the force. Because of the tendency of the binding elements to remain in their closed position, it is difficult to add or remove perforated sheets from the binder without damage to the binding elements or the sheets. Indeed, it was never intended that the user should normally attempt to add or remove pages without the help of a special tool.
The above described class of binding materials has come to be considered permanent for all practical purposes.
To overcome the shortcomings inherent in the devices described above, my prior patent, U.S. Pat. No. 4,374,627, disclosed a ring-type binder having two substantially smooth members being longitudinally movable relative to one another. One member, forming a closure, is provided with a raised projection at one end and an aperture at the other end. The other member, having a plurality of rings or teeth along its length, is provided with an aperture at one end and a projection at the other so that they correspond respectively to the projection and aperture of the closure member. Thus, when the members are aligned the corresponding apertures and projection engage placing the binder in a locked position. Upon application of a separating force by the user, however, the members were movable relative to one another so as to permit the insertion of additional pages.
It will be apparent that after numerous cycles wherein the members are shifted between the open and locked position, that the projections worn due the shear stress exerted thereon. In some cases, this results in the unwanted shifting of the binder members and fracturing of the projections. To improve the functional life of the binder, an improved locking device is required.
One alternative explored, but not patented, was to use one of the ring elements as the locking device by providing an orifice in the closure member for the insertion and reception of one of the plurality of teeth or rings. When inserted in the orifice the ring element prevents the relative movement of the binder members, thereby keeping the binder in a locked position. When additional papers are required, the ring element must first be removed so as to permit movement of the binder members. However, this arrangement was not without problems. If the binder was filled to maximum capacity, or beyond, the additional force exerted on the ring element made removal of the ring from the orifice difficult. Further, the increased stress on the locking ring element caused by cyclical insertion and removal caused breakage rendering the binder inoperable.
It is therefore, the object of the present invention to provided a ring-type binder that overcomes the defects and disadvantages of the prior art ring-type binders.
It is another object of the present invention to provide a improved ring-type binder that is simple in construction, easy to operate and durable.
It is a further object to provide an improved locking device that does not compromise the structural integrity of the ring elements or hinder the functioning of the binder.
These objects, together with other objects and advantages, will be apparent from the following disclosure of the present invention.